The easiest way to try the difference between nic salt and freebase nicotine is to go into a vape shop and buy two premade 10ml juices that include nicotine - 1 of freebase and 1 of nic salt.
Generally nic salts are widely available in 10 and 20mg and freebase in 12 and 18mg so just buy the one closest to the strength you normally vape at.
Personally I have severe problems with freebase nicotine over 6mg strength as I find it harsh on the throat and vaping it leaves my throat sore and scratchy for days, but that is just my experience - others have mentioned that they have problems with nic salt but it's relatively cheap to find out if you just buy a single 10ml bottle.
One thing to be aware of though is nic salt has very little throat hit, if you have been vaping high strength freebase for years it may seem strange because, to me at least, it seems very smooth compared to freebase - it may be easier on your throat until you have fully recovered, or not lol, but it doesn't cost much to find out.